Managing Garden Insects Begins with a Question: Friend or Foe?

[Background music]>>Managing garden insects
begins with a question. “Friend or Foe?” One of the most common
questions that people ask entomologists about
insects in the garden is “How do I kill it?” However, many kinds of insects
are actually helpful in the garden and getting rid of them
can lead to problems. Before you decide whether
an insect is friend or foe, you must first answer
the important question “What is it?” The answer will tell you
if it is a useful partner, a minor problem, or has
the potential to become a serious problem. Once you know what it is,
you can easily learn where it lives, how it
lives and if necessary, the options for
effective management. The most sensible and
intelligent option for managing insect
pests is IPM or Integrated Pest Management. IPM allows us to reduce
reliance on one single method, like the use of pesticides,
which is not always the most effective or environmentally
friendly option. IPM allows us to
make intelligent and thoughtful decisions
about pest management. The steps of IPM are: • Monitor the garden • Identify the problem pest • Evaluate the situation and
predict the impact of the damage • Then make a decision about
the best course of action and
choose your control methods. Insects are the most diverse
creatures in the world and they also play many roles
in the environment. At any given time,
your home garden may have over 1,000 different insects. Some people consider insects
as ‘bugs’ or pests that are annoying and must
be destroyed. It is not possible or even
desirable to get rid of all the insects in the garden. Many insects are garden
friends, others are foes and a wise gardener
knows the difference. Among the million or more
insect species known on earth, less than 3% cause
problems to humankind and can be called ‘pests.’ The other 97% are
either harmless or actually beneficial. Let’s start with some
of the friends or the helpful insects
in your garden. Most people are aware
of beneficial insects that pollinate our crops, and
provide us with products like honey, beeswax and silk. Insects also serve as food for
birds, fish and other animals, so they are important
links in the food chain and for maintaining
ecological balance. Through biological control,
harmful insect populations can be reduced by using
other live organisms, including insects. Sometimes natural enemies are
mass-produced and released. However, in a landscape
or home garden situation, it may be difficult to
introduce, release, or retain commercially-reared predator
insects or parasitoids. So the best thing to do
is conserve the existing natural enemies and avoid
practices that harm them, such as, unnecessary
insecticide use. Predatory insects and
other natural enemies can be attracted to
your garden simply by providing food, water,
and shelter through a diverse array of
plant material. Planting a variety of pollen
and nectar bearing flowers can help conserve and
increase the number of beneficial insects
in your garden. Predatory insects are
especially beneficial in the garden because they
eat harmful insect pests. Predators are generally larger
than their prey and faster. They have to capture and
eat many individuals to complete their life cycle. Birds, amphibians, reptiles,
fish, spiders, and insects are examples of predators
that eat insects. Let’s focus on some
common predators. Spiders are some of the most
common and important predators that can be found in a
landscape or garden. Most are general predators
that feed on a variety of prey. Spiders can be easily
identified by their body shape and eight legs. Although there are several
mites that can cause significant damage to plants, there are also some predatory
mites that prey on pest mites as well as small insects
like whiteflies and thrips. Predatory mites are
similar to pest mites, with 8 legs and no
antennae or wings, but they are often larger,
more colorful and move more rapidly than pest mites. Many of the true bugs
– Heteroptera – are predators and prey on other smaller,
soft-bodied insects like aphids, white flies
and even caterpillars. Assassin bugs are
relatively large. Some can be identified by the
wheel-like structure on their back and are often called
‘Wheel bugs’ because of this. Damsel bugs are smaller
and have large eyes. Both of these hunters have a strong proboscis
– long flexible snout- that can pierce the
exoskeleton of other insects. Other true bugs, such as shield bugs,
also known as stink bugs, may be either hunters
or plant eaters, depending on the species. Some insect
eating stinkbugs, unlike their plant-
feeding counterparts, have spine-like extensions
on their shoulders; for example, the
two-spined soldier bug. Plant bugs can
also be pests. Once again, check
the proboscis. The plant eating bugs will
have a delicate proboscis. Population size is
another indicator of the insect’s
dining habits. Often 10 to 100 individuals
of a plant eating species will be found on a plant
whereas populations of a predatory species will
be relatively low, with less than 10
individuals per plant. Green and Brown Lacewings are
very common predators found in gardens and are
fairly easy to identify because of their distinctive
lace-like wing pattern. Adults feed on pollen and
small, soft-bodied insects like aphids, lace bugs,
and mites. Larvae are voracious predators
with powerful sickle-shaped mandibles – grasping
appendages near the mouth. Lacewing eggs are an easy to
identify treat in the garden. Each egg floats above
the leaf surface, supported by a
thread-like strand. This may serve to
prevent cannibalism among the young larvae
as they hatch. Praying Mantids are also large
and powerful predators. They use their strong
front legs to capture and devour their prey. They are easily recognized
and widely praised for their hunting prowess. However, they eat both
friends and foes including other praying
mantids, so they may not be the most dependable
hunter in the garden. Still who can
resist their charms? Several families of beetles
are voracious predators both as larvae
and as adults. Some of these may be common
in your garden such as Ground Beetles, Tiger Beetles
and Rove Beetles. These predators can
be identified by their sickle-shaped
crossing mandibles. Wasps, like paper wasps
and yellow jackets should be welcome in the garden because
they do not attack plants but instead protect them
by feeding primarily on caterpillars. They have strong mandibles
for chewing prey, as well as a proboscis which they use
to suck nectar from flowers. Please do not attempt to
check their mouthparts! They are related to bees
and may sometimes show aggressive behavior by
stinging when disturbed. Give them plenty of space. Flies, such as syrphid
or flower flies and robber flies can be
very important predators. Syrphid flies can be
voracious feeders on aphids and will be attracted
to pest populations even when they
are low in number. They often mimic bees
or wasps and appear to hover in flight
like hummingbirds. Robber flies have
heart-shaped heads with an indentation between
the eyes and a “bearded” face. These flies may also
mimic wasps and bees. They are often seen
capturing prey in flight. You are probably familiar
with parasites, like ticks or fleas. They are generally much
smaller than their hosts and live on or within
the host for part or all of their life cycle. Generally they don’t
kill their hosts. Insect parasitoids
are different. They kill their hosts
by eating them. Adult parasitoids
often lay their eggs inside or on the host. The immature parasitoids
hatch and consume their host
during development. Many insect parasitoids
are found in the order containing wasps,
Hymenoptera. Some are very specific
in prey selection, others prey on a
wide variety of pests. Parasitic wasps attack
caterpillars and aphids. They lay eggs in the host
and when the larvae emerge, they consume the host. These wasps leave behind
mummified hosts. The mummies have darkened
shells with exit holes, from which the adult
parasitoid emerged. Sometimes the parasitoid
will pupate on the host; other species will pupate
near the dead host. Parasitic wasps are also
very effective against scale insects, and when
large numbers of exit holes can be seen on scale insects,
avoid spraying insecticides to conserve these
natural enemies. As every gardener knows, not all garden insects
are beneficial. Insects are often the cause
of the unsightly damage seen on our plants. In many cases, the insect
damage may weaken the plant and predispose
it to diseases. Destructive insects
can be divided into four basic categories
based on the type of damage they cause to plants: chewing, discoloration,
distortion, and die back. Chewed, shredded, torn
and skeletonized leaves, flowers, buds, and fruits
can be symptoms of insect damage on plants. This kind of damage is
caused by insects with cutting and chewing mouthparts. These insects have
powerful mandibles that cut up plant parts. Examples of such insects are caterpillars of
butterflies and moths and larvae of sawflies, larvae and adults of beetles,
and grasshoppers. Discoloration of leaves
by stippling, flecking, bleaching or bronzing,
with no actual damage to the shape or size
of leaves is often caused by insects with piercing
and sucking mouthparts. This damage is caused when the
insects insert their slender, needle-like mouthparts
into the leaf tissue and draw out plant sap. In the process, they’ll also
damage the surrounding cells which results in destruction
of chlorophyll leading to the leaf discoloration. The discoloration begins as
small white flecks or stipples and gradually the entire
leaf may become chlorotic or bleached in appearance. Some insects that cause this
type of damage are lace bugs, aphids, plant hoppers,
white flies, and leaf hoppers. Mites and thrips are
very small and may not be visible with
the naked eye. Sometimes webbing may
be seen in plants affected by mites. Thrips – adults
and juveniles – can be identified
under a microscope. Distortion of plant parts
into abnormal shapes or structures can also be
a sign of insect damage. For example, galls on leaves,
flowers or stems, leaf curling
or cupping and abnormally twisted
leaves or stems. This type of damage can be
caused by different insects like thrips, aphids, larvae
of some wasps and moths, and also gall mites. It is important to note
that some plant diseases can also cause galls. Sometimes twigs, stems,
or branches or even the entire plant appear
to wilt and eventually die. This symptom, called die back,
can be caused by insects. These dead twigs and branches
are retained on the plant. This damage is typical
of scale insects because they are not mobile
and severely deplete the branch or twig
of plant sap. Some moth larvae and
beetles that bore into stems can also
cause this symptom. In addition to damage or
symptoms, insect products, often called signs, such as
fecal spots, honey dew, frass, and cast skins are solid
evidence of their presence and/or activity on the plant. These may not be directly
harmful to the plant and often remain on the plant
for long periods of time even after the
insect has left. Make sure there is an
active infestation on the plant before considering the
application of an insecticide. Sooty mold, a charcoal black
fungus grows on honey dew secreted by sap feeding
insects such as aphids, mealybugs, scales,
and white flies. It is another common
sign of insect activity. Though sooty mold appears
to grow on the plants, it is not a plant disease,
and is a clear indication of an insect infestation. At times, sooty mold can
also grow on other surfaces like in this picture. You can see how the honey dew
dripping from the tree above caused sooty mold on the wall
and road along the tree line. If the insect
is controlled, the sooty mold will
go away on its own. Chewing, distortion,
discoloration and die back symptoms can be caused by a
wide variety of insects and often a single pest may cause
different types of symptoms. Similar symptoms can be
caused by plant disease or even abiotic causes such
as environmental stress, extreme heat, drought,
cold injury or chemicals. Once potential insect
damage has been identified, the next step is to
look for insects. Symptoms and signs alone
do not warrant action. When you see any of these
symptoms, look for insects. Carefully check both
sides of the leaves and carefully study the stems. Look in the branch forks
and all around the flowers. Insects can be
very good at hiding. After locating
suspected pests, the next step is to
identify the host plant. Once you know the
name of the plant, you can easily discover
the common pests associated with it. At this stage in
your diagnosis your County Extension Agent
will be a great resource. Each state has a
Pest Control Handbook that will suggest control
measures if needed. Remember to consider
the severity of the infestation and damage,
plant species involved, and any evidence of predator
or parasitoid activity before applying pesticides. We hope that this video will
help you identify the insect Friends and Foes that you
will commonly encounter in your gardens
and landscapes. You will be amazed at just how
astounding and fascinating the diverse world of
garden insects can be. In fact, if you take the
time to get to know them, you may find you enjoy
your garden insects as much as the plants! © 2012 University of Georgia College of Agricultural
and Environmental Sciences

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